Light-emitting device

ABSTRACT

A light-emitting device includes an inner light-emitting element having an n-sided polygonal shape (n is an integer of 3 or more) in a plan view with a peak emission wavelength in a range of 490 nm to 570 nm; m (m is an integer of 3 or more) outer light-emitting elements with a peak emission wavelength of 430 nm or greater and less than 490 nm; and a first phosphor with a peak emission wavelength in a range of 580 nm to 680 nm covering the inner light-emitting element and the m outer light-emitting elements. Each of n lateral surfaces of the inner light-emitting element faces a corresponding one of the m outer light-emitting elements in a top view.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. 2017-245665, filed Dec. 22, 2017, and JapanesePatent Application No. 2018-076518, filed Apr. 12, 2018. The entiredisclosures of Japanese Patent Application No. 2017-245665 and JapanesePatent Application No. 2018-076518 are incorporated by reference herein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to a light-emitting device.

2. Description of Related Art

Japanese Unexamined Patent Application Publication No. 2007-158296describes a light-emitting device including a blue-light emittingelement, a green-light emitting element, and a red phosphor. A backlightdevice employing such a light-emitting device as a light source isconsidered to have a high color reproducibility.

SUMMARY

However, the light-emitting device in Japanese Unexamined PatentApplication Publication No. 2007-158296 may cause unevenness in emissioncolor because blue light and green light emitted from corresponding onesof the light-emitting elements has a high straightness.

Accordingly, certain embodiments of the present invention has an objectto provide a light-emitting device with reduced unevenness in emissioncolor.

A light-emitting device includes an inner light-emitting element havingan n-sided polygonal shape (n is an integer of 3 or more) in a plan viewwith a peak emission wavelength in a range of 490 nm to 570 nm; m (m isan integer of 3 or more) outer light-emitting elements with a peakemission wavelength of 430 nm or greater and less than 490 nm; and afirst phosphor with a peak emission wavelength in a range of 580 nm to680 nm covering the inner light-emitting element and the m outerlight-emitting elements. Each of n lateral surfaces of the innerlight-emitting element faces a corresponding one of the m outerlight-emitting elements in a top view.

Certain embodiments of the present invention allows for providing alight-emitting device with reduced unevenness in emission color.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic top view of a light-emitting device according toa first embodiment of the present disclosure.

FIG. 1B is a schematic bottom view of the light-emitting deviceaccording to the first embodiment of the present disclosure.

FIG. 1C is a schematic end view taken along the line 1C-1C of FIG. 1A.

FIG. 2A is a schematic top view of a variant example of a light-emittingdevice of the present disclosure.

FIG. 2B is a schematic top view of another variant example of alight-emitting device of the present disclosure.

FIG. 2C is a schematic top view of even another variant example of alight-emitting device of the present disclosure.

FIG. 2D is a schematic top view of still another variant example of alight-emitting device of the present disclosure.

FIG. 2E is a schematic top view of yet another variant example of alight-emitting device of the present disclosure.

FIG. 2F is a schematic top view of still another variant example of alight-emitting device of the present disclosure.

FIG. 3 is a schematic top view of a light-emitting device according to asecond embodiment of the present disclosure.

FIG. 4A is a schematic top view of a light-emitting device according toa third embodiment of the present disclosure.

FIG. 4B is a schematic end view taken along the line 4B-4B of FIG. 4A.

FIG. 5A is a schematic top view of a light-emitting device according tothe present disclosure and a lens member.

FIG. 5B is a schematic end view taken along the line 5B-5B of FIG. 5A.

DETAILED DESCRIPTION OF EMBODIMENTS

Detailed descriptions are provided below on the basis of theaccompanying drawings. Portions with the same reference numeral in aplurality of drawings represents the same or equivalent portions ormembers.

Descriptions below are intended to exemplify a light-emitting device togive a concrete form to the technical idea of the present invention andare not intended to limit the present invention thereto. Unlessspecifically stated otherwise, sizes, materials, shapes, and relativepositions of constituent components described below are not intended tolimit the scope of the present invention thereto but rather are intendedto describe examples thereof. The descriptions below may include terms(such as “up”, “down”, and other terms inclusive of these terms)indicating specific directions or positions. These terms are used tofacilitate understanding of relative directions or positions in thereferenced drawings. Sizes or positional relationships of membersillustrated in the drawings may be exaggerated in order to facilitateunderstanding. The relationships between color names and chromaticitycoordinates, the relationships between wavelength regions of light andcolor names of monochromatic lights, and the like are based on JIS Z8110.

First Embodiment

FIG. 1A is a schematic top view of a light-emitting device 100 accordingto a first embodiment. FIG. 1B is a schematic bottom view of thelight-emitting device 100. FIG. 1C is a schematic end view taken alongthe line 1C-1C of FIG. 1A. In FIG. 1A, illustrations of a first phosphor7 and a sealing member 40 are omitted. The light-emitting device 100includes an inner light-emitting element 11 having an n-sided polygonalshape (n is an integer of 3 or more) in a plan view with a peak emissionwavelength in the range of 490 nm to 570 nm, m (m is an integer of 3 ormore) outer light-emitting elements 12 with a peak emission wavelengthof 430 nm or greater and less than 490 nm, and the first phosphor 7 witha peak emission wavelength in the range of 580 nm to 680 nm.

The inner light-emitting element 11 has n lateral surfaces. The innerlight-emitting element 11 has, for example, a triangular, quadrilateral,or hexagonal shape in a top view and has three, four, or six lateralsurfaces. The inner light-emitting element 11 is a light-emittingelement with a peak emission wavelength in the range of 490 nm to 570 nmthat emits green light.

The m outer light-emitting elements 12 are, for example, three outerlight-emitting elements, four outer light-emitting elements, or five ormore outer light-emitting elements. Each of the m outer light-emittingelements 12 faces at least one of the n lateral surfaces of the innerlight-emitting element 11 in a top view. In other words, the innerlight-emitting element 11 is disposed such that each of the n lateralsurfaces of the inner light-emitting element 11 faces a correspondingone of the m outer light-emitting elements 12. Each of the m outerlight-emitting elements 12 is a light-emitting element with a peakemission wavelength of 430 nm or greater and less than 490 nm that emitsblue light.

The light-emitting device 100 shown in FIG. 1A is a light-emittingdevice in the case where n=m=4. The light-emitting device 100 includesan inner light-emitting element 11 having a quadrilateral planar shapeand four outer light-emitting elements 12. The inner light-emittingelement 11 and the four outer light-emitting elements 12 are located onor above the bottom surface of a recess 2. The inner light-emittingelement 11 has a first lateral surface 111, a second lateral surface 112opposite to the first lateral surface 111, a third lateral surface 113connected to the first lateral surface 111 and the second lateralsurface 112, and a fourth lateral surface 114 opposite to the thirdlateral surface 113 in a top view. The four outer light-emittingelements 12 of the light-emitting device 100 includes, a firstlight-emitting element 12 a, a second light-emitting element 12 b, athird light-emitting element 12 c, and a fourth light-emitting element12 d. The first light-emitting element 12 a faces the first lateralsurface 111, the second light-emitting element 12 b faces the secondlateral surface 112, the third light-emitting element 12 c faces thethird lateral surface 113, and the fourth light-emitting element 12 dfaces the fourth lateral surface 114.

With the m outer light-emitting elements 12 disposed such that the outerlight-emitting elements 12 face the lateral surfaces of the innerlight-emitting element 11, the color of light emitted from the lateralsurfaces of the inner light-emitting element 11 can be easily mixed withthe color of light emitted from the m outer light-emitting elements 12.By sufficiently mixing the color of light emitted from the innerlight-emitting element 11 with the color of light emitted from the mouter light-emitting elements 12, unevenness in emission color of thelight-emitting device can be easily reduced. The expression “face” asused herein encompasses not only the case where all of the lateralsurfaces of the inner light-emitting element 11 faces an entirety of acorresponding one of the lateral surfaces of each of the outerlight-emitting elements 12, but also the case where a portion of alateral surface of the inner light-emitting element 11 faces acorresponding one of the lateral surfaces of a corresponding one of theouter light-emitting elements 12, and the case where a lateral surfaceof the inner light-emitting element 11 faces a portion of acorresponding one of the lateral surfaces of a corresponding one of theouter light-emitting elements 12. Each of the outer light-emittingelements 12 preferably faces 50% or more, more preferably 75% or more,further preferably 100% (i.e., an entirety) of a respective one of thelateral surfaces of the inner light-emitting element 11. With thisstructure, the colors of light emitted from the inner light-emittingelement 11 and light emitted from the outer light-emitting elements canbe effectively mixed.

In the light-emitting device 100 shown in FIG. 1A, in a top view, thethird light-emitting element 12 c and the fourth light-emitting element12 d overlap the extension lines of the diagonal lines of the innerlight-emitting element 11. The third light-emitting element 12 c and thefourth light-emitting element 12 d face at least a portion of the firstlight-emitting element 12 a and the second light-emitting element 12 b,respectively, in addition to corresponding lateral surfaces of the innerlight-emitting element 11 in a top view. With this structure, forexample, the color of light emitted from the corner portions of theinner light-emitting element 11 can be effectively mixed with the colorof light emitted from the outer light-emitting elements.

It is preferable that a distance in a top view between each of the outerlight-emitting elements and the inner light-emitting element 11 besmall. With this structure, the colors of light emitted from the innerlight-emitting element 11 and light emitted from the outerlight-emitting elements can be effectively mixed. A distance betweeneach of the outer light-emitting elements and the inner light-emittingelement 11 is, for example, 100 μm or less, preferably 50 μm or less,more preferably 40 μm or less. Also, the distance between each of theouter light-emitting elements and the inner light-emitting element 11is, for example, one half or less, preferably one quarter or less, ofthe height of a respective one of the outer light-emitting elements orthe inner light-emitting element 11.

The inner light-emitting element 11 and the m outer light-emittingelements 12 are preferably connected in series. With this structure, alight-emitting device that exhibits high emission intensity when apredetermined current is applied can be provided. In the light-emittingdevice 100 shown in FIG. 1A, a first lead 51 is connected to acorresponding one of electrodes of the first light-emitting element 12 aby a wire, and the other electrode of the first light-emitting element12 a is connected to a corresponding one of electrodes of the fourthlight-emitting element 12 d by a wire. Also, the other electrode of thefourth light-emitting element 12 d is connected to a corresponding oneof electrodes of the inner light-emitting element 11 by a wire, and theother electrode of the inner light-emitting element 11 is connected to acorresponding one of electrodes of the third light-emitting element 12 cby a wire. In addition, the other electrode of the third light-emittingelement 12 c is connected to a corresponding one of electrodes of thesecond light-emitting element 12 b by a wire, and the other electrode ofthe second light-emitting element 12 b is connected to a second lead 52by a wire.

In the light-emitting device of the present disclosure, the manner ofelectrically connecting the light-emitting elements is not limited tothe above manner. The inner light-emitting element 11 and the m outerlight-emitting elements 12 may be all connected in parallel, or parallelconnections and series connections may be combined.

The light-emitting device 100 includes the first phosphor 7 with a peakemission wavelength in the range of 580 nm to 680 nm. For example, thefirst phosphor 7 is adapted to absorb blue light emitted from the outerlight-emitting elements and to emit red light. It is preferable that thefirst phosphor 7 be a phosphor that adapted to emit almost no red lightwhen it absorbs green light emitted from the inner light-emittingelement 11. In other words, it is preferable that the first phosphor 7be a phosphor that does not substantially convert green light into redlight. Using a phosphor that is less likely to perform wavelengthconversion of green light for the first phosphor 7 allows for designingthe output balance of the light-emitting device only in consideration ofwavelength conversion of blue light emitted from the m outerlight-emitting elements 12. Accordingly, designing of the light-emittingdevice can be facilitated.

Such preferable examples of the first phosphor 7 include phosphorsdescribed below. The first phosphor 7 can include a first-type phosphorand/or a second-type phosphor described below.

The first-type phosphor is a red phosphor having a compositionrepresented by the following general formula (I).A₂MF₆:Mn⁴⁺  (I)

In the above general formula (I), A is at least one selected from thegroup consisting of K, Li, Na, Rb, Cs, and NH⁴⁺, and M is at least oneelement selected from the group consisting of the group IV elements andthe group XIV elements.

The “group IV elements” herein refers to titanium (Ti), zirconium (Zr),and hafnium (Hf). The “group XIV elements” herein refers to silicon(Si), germanium (Ge), tin (Sn), and lead (Pb).

Specific examples of the first-type phosphor include K₂SiF₆:Mn⁴⁺,K₂(Si,Ge)F₆:Mn⁴⁺, and K₂TiF₆:Mn⁴⁺.

The second-type phosphors is a phosphor having a composition representedby 3.5MgO.0.5MgF₂.GeO₂:Mn⁴⁺ or a phosphor having a compositionrepresented by the following general formula (II).(x−a)MgO.a(Ma)O.b/2(Mb)₂O₃ .yMgF₂ .c(Mc)X₂.(1−d−e)GeO₂ .d(Md)O₂.e(Me)₂O₃:Mn⁴⁺  (II)

In the above general formula (II), Ma is at least one selected from Ca,Sr, Ba, and Zn; Mb is at least one selected from Sc, La, and Lu; Mc isat least one selected from Ca, Sr, Ba, and Zn; X is at least oneselected from F and Cl; Md is at least one selected from Ti, Sn, and Zr;and Me is at least one selected from B, Al, Ga, and In. Also, x, y, a,b, c, d, and e satisfy 2≤x≤4, 0≤y≤2, 0≤a≤1.5, 0≤b≤1, 0≤c≤2, 0≤d≤0.5, and0≤e≤1.

It is preferable that the light-emitting device 100 include a package 10having the recess 2 as shown in FIG. 1A. With the inner light-emittingelement 11 and the m outer light-emitting elements 12 on the bottomsurface of the recess 2, the colors of light emitted from thelight-emitting elements can be easily mixed.

The package 10 shown in FIG. 1A and FIG. 1B includes a resin portion 30,the first lead 51, and the second lead 52. A portion of the uppersurface of the first lead 51 and a portion of the upper surface of thesecond lead 52 is exposed from the resin portion 30 on the bottomsurface of the recess 2.

The package 10 has an upper surface 80 a and a lower surface 80 bopposite to the upper surface 80 a. The package 10 has a substantiallyrectangular external shape in a top view and also has a first outerlateral surface 81, a second outer lateral surface 82 opposite to thefirst outer lateral surface 81, a third outer lateral surface 83, and afourth outer lateral surface 84 opposite to the third outer lateralsurface 83.

The lower surface 80 b of the package 10 serves as a mounting surface tobe mounted on a mounting board. The first lead 51 and the second lead 52are exposed from the resin portion 30 on the lower surface 80 b of thepackage 10.

Members used for the light-emitting device 100 according to certainembodiments of the present invention will be described below in detail.

Inner Light-Emitting Element and Outer Light-Emitting Elements

The light-emitting device 100 includes the inner light-emitting element11 having the n-sided polygonal shape (n is an integer of 3 or more) ina plan view and the m (m is an integer of 3 or more) outerlight-emitting elements 12. The inner light-emitting element 11 and them outer light-emitting elements 12 function as light sources of thelight-emitting device 100. Light-emitting diode elements or the like canbe used for the inner light-emitting element 11 and the m outerlight-emitting elements 12. Nitride semiconductors(In_(x)Al_(y)Ga_(1-x-y)N, where 0≤x, 0≤y, and x+y≤1), which can emitvisible light, are preferably used.

The inner light-emitting element 11 is a light-emitting element with apeak emission wavelength in the range of 490 nm to 570 nm that emitsgreen light. Each of the m outer light-emitting elements 12 is alight-emitting element with a peak emission wavelength of 430 nm orgreater and less than 490 nm that emits blue light. A light-emittingelement having a half band-width of 40 nm or less, more preferably 30 nmor less, is preferably used for each of the inner light-emitting element11 and the m outer light-emitting elements 12. With such alight-emitting element, blue and green light having sharp emission peakscan be easily obtained. Accordingly, for example, in the case where thelight-emitting device 100 is used as a light source for a liquid-crystaldisplay, a liquid-crystal display with good color reproducibility can beprovided.

The inner light-emitting element 11 and the outer light-emittingelements 12 can be bonded to the package 10 or a mounting board usingdie-bonding members. Examples of the die-bonding members include resinssuch as thermosetting resins and thermoplastic resins; solders such astin-bismuth, tin-copper, tin-silver, and gold-tin solders; eutecticalloys such as alloys containing mainly Au and Sn, alloys containingmainly Au and Si, and alloys containing mainly Au and Ge;electrically-conductive pastes of silver, gold, and palladium; bumps;anisotropic conductive materials; and brazing materials oflow-melting-point metals.

The die-bonding members can contain a light-reflective substance with ahigh light reflectance or a light-absorbing material that is likely toabsorb light, in accordance with the purpose. Examples of thelight-reflective substance include titanium oxide, zinc oxide, siliconoxide, zirconium oxide, aluminum oxide, and aluminum nitride. Examplesof the light-absorbing material include carbon materials such asacetylene black, activated carbon, and graphite; transition metal oxidessuch as iron oxide, manganese dioxide, cobalt oxide, and molybdenumoxide; and colored organic pigments.

With a light-reflective substance or a light-absorbing materialcontained in the die-bonding members, for example, the chromaticity oflight emitted from the light-emitting device 100 can be close to adesired chromaticity. More specifically, the more the green lightcomponent of light emitted from the light-emitting device 100, thegreater the y value of the chromaticity of light emitted from thelight-emitting device 100 in the 1931 CIE chromaticity diagram tends to,and the less the green light component of light emitted from thelight-emitting device 100, the smaller the y value tends to. In thisregard, in the case where a light-emitting device configured to emitlight having a chromaticity with a high y value is to be provided, forexample, the die-bonding members for the inner light-emitting element 11(i.e., green light-emitting element) can contain a light-reflectivesubstance. This structure allows for efficiently extracting lightemitted from the inner light-emitting element 11, and a light-emittingdevice configured to emit light having a chromaticity with a high yvalue can be therefore easily provided. Similarly, in the case where alight-emitting device configured to emit light having a chromaticitywith a low y value is to be provided, for example, the die-bondingmembers for the inner light-emitting element 11 (i.e., greenlight-emitting element) can contain a light-absorbing material. Aportion of light emitted downward from the inner light-emitting element11 is thus absorbed by the light-absorbing material, and the green lightcomponent of the light-emitting device 100 can be reduced. Alight-emitting device configured to emit light having a chromaticitywith a low y value can be therefore easily provided.

Instead of or in addition to the die-bonding members for the innerlight-emitting element 11, the die-bonding members for the outerlight-emitting elements 12 may contain a light-reflective substance or alight-absorbing material depending on the purpose. In the case where aplurality of inner light-emitting elements 11 or a plurality of outerlight-emitting elements 12 are disposed, for example, all thedie-bonding members for the inner light-emitting elements 11 may containa light-reflective substance, or some of the die-bonding members for theinner light-emitting elements 11 may contain a light-reflectivesubstance. In addition, the contents of the light-reflective substanceor the like in the die-bonding members may be the same in alldie-bonding members, or may be different from one another or among someof the die-bonding members.

The light-emitting device 100 shown in FIG. 1A includes the innerlight-emitting element 11 having a quadrilateral planar shape and fourouter light-emitting elements 12. The light-emitting device according tothe present disclosure is not limited to this structure. In thelight-emitting device 100, the planar shape of the inner light-emittingelement 11, the number m of the outer light-emitting elements 12, thearrangement of the inner light-emitting element 11 and the m outerlight-emitting elements 12, and the like can be changed in accordancewith the purpose and the intended use.

Light-emitting devices shown in FIG. 2A to FIG. 2F are variant examplesof the light-emitting device 100. In FIG. 2A to FIG. 2F, illustrationsof the wires and the sealing members 40 are omitted.

Light-emitting devices 100A and 100B shown in FIG. 2A and FIG. 2B differfrom the light-emitting device 100 mainly in the planar shape of theinner light-emitting element 11 and the number (i.e., value of m) of theouter light-emitting elements 12. The light-emitting device 100A in FIG.2A is a light-emitting device in the case where n=m=3. Thelight-emitting device 100A includes an inner light-emitting element 11having a triangular planar shape and three outer light-emittingelements, which include a first light-emitting element 12 a, a secondlight-emitting element 12 b, and a third light-emitting element 12 c.Each of the first light-emitting element 12 a, the second light-emittingelement 12 b, and the third light-emitting element 12 c faces arespective one of the lateral surfaces of the inner light-emittingelement 11. In the light-emitting device 100A, each single outerlight-emitting element faces a corresponding one of the lateral surfacesof the inner light-emitting element 11. This allows for effectivelymixing the color of light emitted from the lateral surfaces of the innerlight-emitting element 11 and the color of light emitted from the outerlight-emitting elements.

The light-emitting device 100B in FIG. 2B is a light-emitting device inthe case where n=m=6. The light-emitting device 100B includes an innerlight-emitting element 11 having a hexagonal planar shape and six outerlight-emitting elements, which include a first light-emitting element 12a, a second light-emitting element 12 b, a third light-emitting element12 c, a fourth light-emitting element 12 d, a fifth light-emittingelement 12 e, and a sixth light-emitting element 12 f. Each of the firstto sixth light-emitting elements 12 a to 12 f faces a respective one ofthe lateral surfaces of the inner light-emitting element 11. In thelight-emitting device 100B, each outer light-emitting element faces acorresponding one of the lateral surfaces of the inner light-emittingelement 11. This allows for effectively mixing the color of lightemitted from the lateral surfaces of the inner light-emitting element 11and the color of light emitted from the outer light-emitting elements. Ashape of the outline of the m outer light-emitting elements 12 in a topview in the light-emitting device 100B is closer to a circle than thatin the light-emitting device 100. Accordingly, light emitted from theinner light-emitting element 11 and the m outer light-emitting elements12 is efficiently extracted to the outside from the light-emittingdevice 100B having the recess 2 with a circular opening. Further, thelight-emitting device 100B includes a greater number of outerlight-emitting elements than the light-emitting device 100, which allowsthe electric current passing through each light-emitting element to besmaller than that in the light-emitting device 100 when operating on thesame electric power. The light-emitting device 100B can be thereforesafely handled.

A light-emitting device 100C shown in FIG. 2C differs from thelight-emitting device 100 mainly in that the inner light-emittingelement 11 and the m outer light-emitting elements 12 are arranged to beinclined with respect to a corresponding one of outer lateral surfaces 9of the package 10 in a top view. The light-emitting device 100C is alight-emitting device in the case where n=m=4. The light-emitting device100C includes an inner light-emitting element 11 having a quadrilateralplanar shape and four outer light-emitting elements, which include afirst light-emitting element 12 a, a second light-emitting element 12 b,a third light-emitting element 12 c, and a fourth light-emitting element12 d. The inner light-emitting element 11 and the four outerlight-emitting elements are arranged to be inclined with respect to theouter lateral surface 9 of the package 10 in a top view. With thisarrangement, a distance between each of the inner lateral surfaces ofthe recess 2 and a corresponding one of the lateral surfaces of acorresponding one of the outer light-emitting elements can be largerthan that in the light-emitting device 100, so that, for example,deterioration of the resin portion 30 constituting the inner lateralsurfaces of the recess 2 due to heat and light generated from the outerlight-emitting elements can be reduced.

A light-emitting device 100D shown in FIG. 2D differs from thelight-emitting device 100 mainly in that each of the lateral surfaces ofthe inner light-emitting element 11 are not parallel to a correspondingone of the lateral surfaces of a corresponding one of the outerlight-emitting elements facing the corresponding one of the lateralsurfaces of the inner light-emitting element 11. The light-emittingdevice 100D is a light-emitting device in the case where n=m=4. Thelight-emitting device 100D includes an inner light-emitting element 11having a quadrilateral planar shape and four outer light-emittingelements, which include a first light-emitting element 12 a, a secondlight-emitting element 12 b, a third light-emitting element 12 c, and afourth light-emitting element 12 d. The inner light-emitting element 11has the first lateral surface 111, the second lateral surface 112, thethird lateral surface 113, and the fourth lateral surface 114. The firstlateral surface 111 of the inner light-emitting element 11 faces both acorresponding one of the lateral surfaces of the first light-emittingelement 12 a and a corresponding one of the lateral surfaces of thesecond light-emitting element 12 b. The second lateral surface 112 ofthe inner light-emitting element 11 faces both a corresponding one ofthe lateral surfaces of the second light-emitting element 12 b and acorresponding one of the lateral surfaces of the third light-emittingelement 12 c. The third lateral surface 113 of the inner light-emittingelement 11 faces both a corresponding one of the lateral surfaces of thethird light-emitting element 12 c and a corresponding one of the lateralsurfaces of the fourth light-emitting element 12 d. The fourth lateralsurface 114 of the inner light-emitting element 11 faces both acorresponding one of the lateral surfaces of the first light-emittingelement 12 a and a corresponding one of the lateral surfaces of thefourth light-emitting element 12 d. The first lateral surface 111, thesecond lateral surface 112, the third lateral surface 113, and thefourth lateral surface 114 are arranged to be inclined with respect tocorresponding ones of the lateral surfaces of the first to fourthlight-emitting elements 12 a to 12 d, respectively. With thisarrangement, a distance between the inner light-emitting element 11 andeach of the outer light-emitting elements in the light-emitting device100D can be larger than that in the light-emitting device 100, so thatpossibility of occurrence of deterioration of the sealing member betweenthe inner light-emitting element 11 and the outer light-emittingelements due to light and heat generated from the light-emittingelements can be reduced.

A light-emitting device 100E shown in FIG. 2E differs from thelight-emitting device 100 mainly in that n m. The light-emitting device100E shown in FIG. 2E is a light-emitting device in the case where n=6and m=4. The light-emitting device 100E includes an inner light-emittingelement 11 having a hexagonal planar shape, and four outerlight-emitting elements, which include a first light-emitting element 12a, a second light-emitting element 12 b, a third light-emitting element12 c, and a fourth light-emitting element 12 d. The number of the outerlight-emitting elements in the light-emitting device 100E can be smallerthan in a light-emitting device including a single outer light-emittingelement for each of the lateral surfaces of the inner light-emittingelement 11. Accordingly, an inexpensive light-emitting device withreduced unevenness in color can be provided. Further, a distance betweenthe inner light-emitting element 11 and each of the outer light-emittingelements in the light-emitting device 100E is larger than that in thelight-emitting device 100, so that the possibility of occurrence ofdeterioration of the sealing member between the inner light-emittingelement 11 and the outer light-emitting elements due to light and heatgenerated from the light-emitting elements can be reduced.

A light-emitting device 100F shown in FIG. 2F is a light-emitting devicein the case where n=m=3. The light-emitting device 100F includes aninner light-emitting element 11 having a triangular planar shape andthree outer light-emitting elements each having a quadrilateral planarshape: a first light-emitting element 12 a, a second light-emittingelement 12 b, and a third light-emitting element 12 c. Each of the firstlight-emitting element 12 a, the second light-emitting element 12 b, andthe third light-emitting element 12 c faces a respective one of thelateral surfaces of the inner light-emitting element 11. In thelight-emitting device 100F, in a top view, a length d1 of a side of eachof the first light-emitting element 12 a, the second light-emittingelement 12 b, and the third light-emitting element 12 c facing the innerlight-emitting element 11 is preferably longer than a length d2 of acorresponding side of the sides of the inner light-emitting element 11.With this structure of the light-emitting device 100F, for example, thecolor of light laterally emitted from the inner light-emitting element11 can be efficiently mixed with the color of light emitted from theouter light-emitting elements. Accordingly, a light-emitting device witha smaller unevenness in color can be provided.

First Phosphor

The light-emitting device 100 includes the first phosphor 7 thatperforms wavelength-conversion of light emitted from the light-emittingelements. The first phosphor 7 is a phosphor with a peak emissionwavelength in the range of 580 nm to 680 nm. The first phosphor 7 iscontained in, for example, a resin material such as a silicone resin.The resin material can be formed by printing, potting, or spraying.Alternatively, the first phosphor 7 may be contained in, for example, aresin member in a form of a sheet or a block, glass, or a ceramic, andthe resin member or the like may be applied using an adhesive. Also, thefirst phosphor 7 may be formed by electrophoretic deposition.

For example, a (Sr,Ca)AlSiN₃:Eu, K₂SiF₆:Mn⁴⁺, or3.5MgO.0.5MgF₂.GeO₂:Mn⁴⁺ phosphor can be used for the first phosphor 7.In particular, a K₂SiF₆:Mn⁴⁺ phosphor can be preferably used. A phosphorthat shows a narrow half band-width is preferably used for the firstphosphor 7. With such a phosphor, for example, in the case where thelight-emitting device 100 is used as a light source for a liquid-crystaldisplay device, a liquid-crystal display device with good colorreproducibility can be provided. The half band-width of the firstphosphor 7 is, for example, 30 nm or less, preferably 15 nm or less.

In addition to the first phosphor 7, the light-emitting device 100 canfurther include a phosphor other than the first phosphor 7. Examples ofthe phosphor include (Ca,Sr,Ba)₅(PO₄)₃(Cl,Br):Eu,Si_(6-z)Al_(z)O_(z)N_(8-z):Eu(0<z<4.2), (Sr,Ca,Ba)₄Al₁₄O₂₅:Eu,(Ca,Sr,Ba)₈MgSi₄O₁₆(F,Cl,Br)₂:Eu, (Y,Lu,Gd)₃(Al,Ga)₅O₁₂:Ce,Ca₃Sc₂Si₃O₁₂:Ce, and CaSc₂O₄:Ce phosphors.

Sealing Member

The light-emitting device 100 can include the sealing member 40 thatcontains the first phosphor 7 and covers the inner light-emittingelement 11 and the m outer light-emitting elements 12. The sealingmember 40 can protect the light-emitting elements and other componentsfrom external force, dust, and water. The sealing member 40 preferablytransmits 60% or more, further preferably 90% or more, of light emittedfrom the light-emitting elements. A thermosetting resin or athermoplastic resin can be used for a resin material to serve as thebase material for the sealing member 40. For example, a silicone resin,an epoxy resin, an acrylic resin, or a resin containing one or more ofthe above resins can be used. The sealing member may be constituted of asingle layer or a plurality of layers. Also, light scattering particlessuch as titanium oxide, silicon oxide, zirconium oxide, and aluminumoxide may be dispersed in the sealing member 40. The light scatteringparticles may have crushed, spherical, hollow, or porous shapes.

Package

The light-emitting device 100 can include the package 10. The package 10is a base on which the light-emitting elements are to be disposed. Thepackage 10 includes at least a matrix and a plurality of leads (aplurality of electrode portions). The package 10 preferably has therecess 2. With the inner light-emitting element 11 and the m outerlight-emitting elements 12 disposed on the bottom surface of the recess2, unevenness in color of the light-emitting device can be easilyreduced. Examples of the material of the base material of the package 10include ceramics such as aluminum oxide and aluminum nitride, resins(such as silicone resins, modified silicone resins, epoxy resins,modified epoxy resins, unsaturated polyester resins, phenolic resins,polycarbonate resins, acrylic resins, trimethylpentene resin,polynorbornene resin, and hybrid resins each containing one or more ofthe above resins), pulp, glass, and composite materials of thesematerials.

The external shape of the package 10 in a top view is, for example, aquadrilateral shape with a dimension of 3.0 mm×1.4 mm, 2.5 mm×2.5 mm,3.0 mm×3.0 mm, or 4.5 mm×4.5 mm. The external shape of the package 10 ina top view is not limited to a quadrilateral shape but may be anotherpolygonal shape or an elliptic shape.

For the package 10, the package used in the light-emitting device 100shown in FIG. 1A, which includes the resin portion 30, the first lead51, and the second lead 52, can be preferably used. This structureallows for providing an inexpensive light-emitting device with high heatdissipation performance. Although the first lead 51 and the second lead52 do not extend outward from the resin portion 30 on the outer lateralsurfaces of the package 10 in the light-emitting device 100 shown inFIG. 1A, the light-emitting device according to the present embodimentis not limited to thereto. In other words, the first lead 51 and thesecond lead 52 may extend outward from the resin portion 30 at the outerlateral surfaces of the package 10. This structure allows forefficiently dissipating heat generated from the light-emitting elementsinto the outside.

Resin Portion

A thermosetting resin or a thermoplastic resin can be used for the resinmaterial to serve as the base material of the resin portion 30. Specificexamples of the resin material include epoxy resin compounds, siliconeresin compounds, modified epoxy resin compositions such assilicone-modified epoxy resins, modified silicone resin compounds suchas epoxy-modified silicone resins, modified silicone resin compounds,unsaturated polyester resins, saturated polyester resins, polyimideresin compounds, and modified polyimide resin compounds; resins such aspolyphthalamide (PPA), polycarbonate resins, poly(phenylene sulfide)(PPS), liquid crystal polymers (LCPs), ABS resins, phenolic resins,acrylic resins, and PBT resins. In particular, a thermosetting resin,such as epoxy resin compounds and silicone resin compounds, having goodresistance to heat and light is preferably used for the resin materialof the resin portion 30.

It is preferable that the resin portion 30 contain a light-reflectivesubstance mixed in the resin material to serve as the base material. Forthe light-reflective substance, a member that is less likely to absorblight emitted from the light-emitting elements and greatly differs inrefractive index from the resin material to serve as the base materialis preferable. Examples of such a light-reflective substance includetitanium oxide, zinc oxide, silicon oxide, zirconium oxide, aluminumoxide, and aluminum nitride.

First Lead and Second Lead

The first lead 51 and the second lead 52 is electrically conductive andfunction as electrodes used for supplying electricity to thelight-emitting elements. For a base portion of the first lead 51 and thesecond lead 52, for example, metals such as copper, aluminum, gold,silver, iron, nickel, alloys of these metals, phosphor bronze, orcopper-iron alloys can be used. A single layer or a layered structure(such as a clad material) may be employed. It is particularly preferablethat copper, which is inexpensive and has high heat dissipationperformance, be used for the base portion.

The first lead 51 and/or the second lead 52 may include metal layers onthe surfaces of the base member. The metal layers contain, for example,silver, aluminum, nickel, palladium, rhodium, gold, copper, or an alloyof these metals. The metal layers may be disposed on the entirety of thesurfaces of the first lead 51 and the second lead 52, or a part of asurface of the first lead 51 and/or a surface of the second lead 52. Themetal layer formed on the upper surface of the first lead 51 and/or theupper surface of the second lead 52 may be different from the metallayer formed on the lower surface of the first lead 51 and/or the uppersurface of the second lead 52. For example, the metal layer formed onthe upper surface of each of the first and second leads 51 and 52 has alayered structure including nickel and silver layers, and the metallayer formed on the lower surface of each of the first and second leads51 and 52 does not include a nickel layer.

In the case where metal layers containing silver are formed on anoutermost surface of the first lead 51 and/or an outermost surface ofthe second lead 52, it is preferable that a protective layer made ofsilicon oxide or the like be disposed on a surfaces of each of the metallayers containing silver. This structure allows for reducingdiscoloration of the metal layer containing silver due to sulfurcomponents and the like in the atmosphere. The protective layers can beformed by a vacuum process such as sputtering, but other known methodsmay be employed alternatively.

The package 10 includes at least two electrodes (such as the first lead51 and the second lead 52). The package 10 may include three or moreelectrodes. The package 10 may include, for example, a third lead inaddition to the first lead 51 and the second lead 52. The third lead mayfunction as a heat dissipating member or, similarly to the first lead 51and the second lead 52, may function as an electrode.

The light-emitting device 100 may not include the package 10.

Second Embodiment

FIG. 3 is a schematic top view of a light-emitting device 200 accordingto a second embodiment. In FIG. 3, illustrations of the first phosphor 7and the sealing member 40 are omitted. The light-emitting device 200differs from the light-emitting device 100 according to the firstembodiment mainly in that a plurality of green light-emitting elementsconstitute the inner light-emitting element 11. The light-emittingdevice 200 includes inner light-emitting elements 11 each having ann-sided polygonal shape (n is an integer of 3 or more) in a plan viewwith a peak emission wavelength in the range of 490 nm to 570 nm, m (mis an integer of 3 or more) outer light-emitting elements 12 with a peakemission wavelength of 430 nm or greater and less than 490 nm, and thefirst phosphor 7 with a peak emission wavelength in the range of 580 nmto 680 nm.

The light-emitting device 200 includes a plurality of greenlight-emitting elements constituting the inner light-emitting elements11. Each of the green light-emitting elements includes a light-emittingpart. In the light-emitting device 200, the combination of the greenlight-emitting elements can form a virtual inner light-emitting elementwith an n-sided polygonal shape in a plan view. In the light-emittingdevice 200 shown in FIG. 3, the inner light-emitting elements 11includes a first green light-emitting element 11 a and a second greenlight-emitting element 11 b each having a triangular planar shape. Thefirst green light-emitting element 11 a has the first lateral surface111, the second lateral surface 112, and a lateral surface facing thesecond green light-emitting element 11 b. The second greenlight-emitting element 11 b has the third lateral surface 113, thefourth lateral surface 114, and a lateral surface facing the first greenlight-emitting element 11 a. In other words, the inner light-emittingelements 11 shown in FIG. 3 forms a virtual inner light-emitting elementwith a quadrilateral shape in a plan view having the four outer lateralsurfaces including the first lateral surface 111, the second lateralsurface 112, the third lateral surface 113, and the fourth lateralsurface 114. The light-emitting device 200 further includes, as the mouter light-emitting elements 12, four outer light-emitting elements,which include the first light-emitting element 12 a, the secondlight-emitting element 12 b, the third light-emitting element 12 c, andthe fourth light-emitting element 12 d. In other words, in thelight-emitting device 200 shown in FIG. 3, n=m=4. The firstlight-emitting element 12 a faces the first lateral surface 111 of thefirst green light-emitting element 11 a, the second light-emittingelement 12 b faces the third lateral surface 113 of the second greenlight-emitting element 11 b, the third light-emitting element 12 c facesthe second lateral surface 112 of the first green light-emitting element11 a, and the fourth light-emitting element 12 d faces the fourthlateral surface 114 of the second green light-emitting element 11 b.With this structure, the color of light emitted from correspondinglateral surfaces of the inner light-emitting elements 11 can beeffectively mixed with the color of light emitted from the outerlight-emitting elements. In addition, with the inner light-emittingelements 11 constituted of a plurality of green light-emitting elements,for example, the chromaticity of light emitted from the light-emittingdevice 200 can be easily adjusted by adjusting the number of the greenlight-emitting elements.

Third Embodiment

FIG. 4A is a schematic top view of a light-emitting device 300 accordingto a third embodiment. FIG. 4B is a schematic end view taken along theline 4B-4B of FIG. 4A. In FIG. 4A, illustrations of the first phosphor 7and the sealing member 40 are omitted. The light-emitting device 300differs from the light-emitting device 100 according to the firstembodiment mainly in that a covering member 6 is disposed on the uppersurface of the inner light-emitting element 11.

The light-emitting device 300 includes the covering member 6 on theupper surface of the inner light-emitting element 11. In thelight-emitting device 300 shown in FIG. 4A and FIG. 4B, the coveringmember 6 is located on the upper surface of the inner light-emittingelement 11 but is not located on the upper surfaces of the m outerlight-emitting elements 12. The covering member 6 is located between thesealing member 40 and the upper surface of the inner light-emittingelement.

The covering member 6 is, for example, a resin member containing asecond phosphor 8. It is preferable that the second phosphor 8 be aphosphor adapted to absorb green light emitted from the innerlight-emitting element 11 and to emit light of another color. With thisstructure, the chromaticity of light emitted upward from the innerlight-emitting element 11 can be easily adjusted by adjusting thecontent of the second phosphor 8. For example, in the case where aK₂SiF₆:Mn⁴⁺ phosphor is used for the first phosphor 7, it is preferablethat a (Sr,Ca)AlSiN₃:Eu or (Sr,Ca)LiAl₃N₄:Eu phosphor be used for thesecond phosphor 8. In the case where the K₂SiF₆:Mn⁴⁺ phosphor is usedfor the first phosphor 7, the K₂SiF₆:Mn⁴⁺ phosphor is excited by bluelight emitted from the outer light-emitting elements but is hardlyexcited by green light emitted from the inner light-emitting element 11.Accordingly, the chromaticity (in particular, the x value) of lightemitted upward from the outer light-emitting elements may greatly differfrom the chromaticity (in particular, the x value) of light emittedupward from the inner light-emitting element 11. However, with thecovering member 6 containing a (Sr,Ca)AlSiN₃:Eu or (Sr,Ca)LiAl₃N₄:Euphosphor, which is adapted to be excited by green light, and disposed onthe upper surface of the inner light-emitting element 11, thechromaticity (in particular, the x value) of light emitted upward fromthe inner light-emitting element 11 can be closer to the chromaticity(in particular, the x value) of light emitted upward from the outerlight-emitting elements. Accordingly, unevenness in emission color ofthe light-emitting device 300 is effectively reduced.

In another embodiment, the covering member 6 is, for example, a resinmember containing a light-reflective member such as titanium oxide. Withthe covering member 6 containing titanium oxide or the like and disposedon the upper surface of the inner light-emitting element 11, theproportion of light laterally emitted from the inner light-emittingelement 11 increases. With this structure, the color of light emittedfrom the inner light-emitting element 11 can be effectively mixed withthe color of light emitted from the outer light-emitting elements, eachof which facing a corresponding one of the lateral surfaces of the innerlight-emitting element 11.

The covering member 6 can contain both the second phosphor 8 and alight-reflective member such as titanium oxide.

Configurations of the light-emitting device described in each of thefirst to third embodiments and their variant examples are suitablyapplicable to other embodiments.

The light-emitting device described in each of the first to thirdembodiments and their variant examples can be used for, for example,direct-type backlight sources for liquid-crystal display devices. In thecase where the light-emitting device is used for a direct-type backlightsource, it is preferable that a lens member 13 be disposed over thelight-emitting device as shown in FIG. 5A and FIG. 5B. FIG. 5A is aschematic top view of the light-emitting device 100 and the lens member13. FIG. 5B is a schematic end view taken along the line 5B-5B of FIG.5A. In FIG. 5A and FIG. 5B, the lens member 13 is located over thelight-emitting device 100, and the optical axis of the lens member 13substantially coincides with the optical axis of the light-emittingdevice 100. For example, the lens member 13 can broaden the distributionof light emitted from the light-emitting device, and/or can improve thecolor mixing performance of light emitted from the light-emittingdevice. With this structure, unevenness in luminance and color of lightemitted from the liquid-crystal display can be effectively reduced. Thelight-emitting device described in each of the first to thirdembodiments and their variant examples are not limited to be used fordirect-type backlight sources. The light-emitting devices can be usedfor, for example, edge-type backlight sources.

What is claimed is:
 1. A light-emitting device comprising: an innerlight-emitting element having a quadrilateral shape in a plan view witha peak emission wavelength in a range of 490 nm to 570 nm; four outerlight-emitting elements, each of the four outer light emitting elementsbeing a light-emitting element with a peak emission wavelength of 430 nmor greater and less than 490 nm; and a first phosphor with a peakemission wavelength in a range of 580 nm to 680 nm covering the innerlight-emitting element and the four outer light emitting elements,wherein the inner light-emitting element has a first lateral surface, asecond lateral surface opposite to the first lateral surface, a thirdlateral surface connected to the first lateral surface and the secondlateral surface, and a fourth lateral surface opposite to the thirdlateral surface, wherein the four outer light-emitting elements have afirst light-emitting element having a first element lateral surfacefacing at least a portion of the first lateral surface, a secondlight-emitting element having a second element lateral surface facing atleast a portion of the second lateral surface, a third light-emittingelement having a third element lateral surface facing a whole portion ofthe third lateral surface, and a fourth light-emitting element having afourth element lateral surface facing a whole portion of the fourthlateral surface, wherein the first light-emitting element, the innerlight-emitting element and the second light-emitting element arearranged in parallel with each other in a first direction, wherein thethird light-emitting element, the inner light-emitting element and thefourth light-emitting element are arranged in parallel with each otherin a second direction vertical to the first direction, wherein the firstlight-emitting element is arranged to be spaced apart from the thirdlight-emitting element and the fourth light-emitting element in thefirst direction, and the first light-emitting element is arranged to atleast partially face the third light-emitting element and the fourthlight-emitting element in the second direction.
 2. The light-emittingdevice according to claim 1, wherein, in a top view, each of the thirdlight-emitting element and the fourth light-emitting element faces theinner light-emitting element, at least a portion of the firstlight-emitting element, and at least a portion of the secondlight-emitting element.
 3. The light-emitting device according to claim1, wherein the inner light-emitting element comprises a plurality ofgreen light-emitting elements each comprising a light-emitting part. 4.The light-emitting device according to claim 1, wherein the innerlight-emitting element comprises a plurality of green light-emittingelements each comprising a light-emitting part.
 5. The light-emittingdevice according to claim 1, wherein the inner light-emitting elementcomprises a plurality of green light-emitting elements each comprising alight-emitting part.
 6. The light-emitting device according to claim 2,wherein the inner light-emitting element comprises a plurality of greenlight-emitting elements each comprising a light-emitting part.
 7. Thelight-emitting device according to claim 1, the light-emitting devicefurther comprising a covering member on an upper surface of the innerlight-emitting element.
 8. The light-emitting device according to claim1, wherein the inner light-emitting element and the four outerlight-emitting elements are electrically connected in series.
 9. Thelight-emitting device according to claim 1, the light-emitting devicefurther comprising a package having a recess, wherein the innerlight-emitting element and the four outer light-emitting elements aredisposed on a bottom surface of the recess.
 10. The light-emittingdevice according to claim 1, wherein a lateral surface of each of allthe outer light-emitting elements, which faces the lateral surface ofthe inner light-emitting element, faces 50% or more of the lateralsurface of the inner light-emitting element.
 11. The light-emittingdevice according to claim 1, wherein a lateral surface of each of allthe outer light-emitting elements, which faces the lateral surface ofthe inner light-emitting element, faces 75% or more of the lateralsurface of the inner light-emitting element.
 12. The light-emittingdevice according to claim 1, wherein each of the first light-emittingelement, the second light-emitting element, the third light-emittingelement and the fourth light-emitting elements has a rectangularconfiguration in a top view, and wherein a longitudinal side of eachrectangular configuration faces the lateral surface of the innerlight-emitting element.
 13. The light-emitting device according to claim1, wherein the inner light-emitting element has a rectangularconfiguration in a top view, wherein the first lateral surface and thesecond lateral surface are located at a longitudinal side of therectangular configuration, and wherein the third lateral surface and thefourth lateral surface are located at a lateral side of the rectangularconfiguration.
 14. The light-emitting device according to claim 13,wherein the third light-emitting element has a first facing lateralsurface which faces the third lateral surface, wherein the thirdlight-emitting element and the inner light-emitting element are locatedin a first direction, and wherein a width of the first facing lateralsurface is larger than that of the third lateral surface in a seconddirection which is perpendicular to the first direction.
 15. Thelight-emitting device according to claim 14, wherein an entirety of thethird lateral surface faces the first facing lateral surface in thesecond direction.
 16. The light-emitting device according to claim 1,wherein a portion of a lateral surface of the inner light-emittingelement and a portion of a lateral surface of the first light-emittingelement are aligned with each other.
 17. The light-emitting deviceaccording to claim 16, wherein a portion of a lateral surface of theinner light-emitting element and a portion of a lateral surface of thesecond light-emitting element are aligned with each other.
 18. Thelight-emitting device according to claim 1, wherein the innerlight-emitting element and the m outer light-emitting elements areelectrically connected by a wire.